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Publication numberUS20080302414 A1
Publication typeApplication
Application numberUS 11/984,092
Publication dateDec 11, 2008
Filing dateNov 13, 2007
Priority dateNov 2, 2006
Also published asEP2218105A2, WO2009064331A2, WO2009064331A3
Publication number11984092, 984092, US 2008/0302414 A1, US 2008/302414 A1, US 20080302414 A1, US 20080302414A1, US 2008302414 A1, US 2008302414A1, US-A1-20080302414, US-A1-2008302414, US2008/0302414A1, US2008/302414A1, US20080302414 A1, US20080302414A1, US2008302414 A1, US2008302414A1
InventorsWillem den Boer, Yiwei Lu
Original AssigneeDen Boer Willem, Yiwei Lu
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Front electrode for use in photovoltaic device and method of making same
US 20080302414 A1
Abstract
This invention relates to a front electrode/contact for use in an electronic device such as a photovoltaic device. In certain example embodiments, the front electrode of a photovoltaic device or the like includes a multilayer coating including at least one transparent conductive oxide (TCO) layer (e.g., of or including a material such as tin oxide, ITO, zinc oxide, or the like) and/or at least one conductive substantially metallic IR reflecting layer (e.g., based on silver, gold, or the like). In certain example instances, the multilayer front electrode coating may include one or more conductive metal(s) oxide layer(s) and one or more conductive substantially metallic IR reflecting layer(s) in order to provide for reduced visible light reflection, increased conductivity, cheaper manufacturability, and/or increased infrared (IR) reflection capability.
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Claims(19)
1. A photovoltaic device comprising:
a front substrate;
a first layer comprising one or more of silicon nitride, silicon oxide, silicon oxynitride, and/or tin oxide;
a second layer comprising one or more of titanium oxide and/or niobium oxide, wherein at least the first layer is located between the front substrate and the second layer;
a third layer comprising zinc oxide and/or zinc aluminum oxide;
a conductive layer comprising silver, wherein at least the third layer is provided between the conductive layer comprising silver and the second layer; and
a transparent conductive oxide (TCO) film provided between the conductive layer comprising silver and a semiconductor film of the photovoltaic device.
2. The photovoltaic device of claim 1, wherein the first layer has a refractive index (n) of from about 1.7 to 2.2, the second layer has a refractive index of from about 2.2 to 2.6, and wherein the second layer has a higher refractive index than the first layer.
3. The photovoltaic device of claim 1, wherein the TCO film comprises one or more of zinc oxide, zinc aluminum oxide, tin oxide, indium-tin-oxide, indium zinc oxide, tin antimony oxide, and zinc gallium aluminum oxide.
4. The photovoltaic device of claim 1, further comprising a buffer layer provided between the TCO film and the semiconductor film.
5. The photovoltaic device of claim 1, wherein the semiconductor film comprises a first layer comprising CdS and a second layer comprising CdTe.
6. The photovoltaic device of claim 1, wherein the TCO film comprises first and second layers of or including different metal oxides.
7. The photovoltaic device of claim 1, wherein the second layer comprises an oxide of titanium.
8. The photovoltaic device of claim 1, wherein the first layer comprises one or more of silicon oxide, silicon nitride and silicon oxynitride.
9. The photovoltaic device of claim 1, further comprising a layer comprising an oxide of NiCr and/or an oxide of Ti located over and directly contacting the conductive layer comprising silver.
10. The photovoltaic device of claim 1, wherein the conductive layer comprising silver is from about 3 to 12 nm thick.
11. The photovoltaic device of claim 1, wherein the front substrate and all layers of the photovoltaic device on a front side of the semiconductor film taken together have an IR reflectance of at least about 45% in at least a substantial part of an IR wavelength range of from about 1400-2300 nm.
12. The photovoltaic device of claim 1, wherein the front substrate and all layers of the photovoltaic device on a front side of the semiconductor film taken together have an IR reflectance of at least about 45% in at least a majority of an IR wavelength range of from about 1000-2500 nm.
13. The photovoltaic device of claim 1, wherein the semiconductor film comprises CdS and/or CdTe.
14. The photovoltaic device of claim 1, wherein the semiconductor film comprises a-Si.
15. The photovoltaic device of claim 1, wherein said TCO film comprises a first layer comprising a first metal oxide and a second layer comprising a second metal oxide, the first layer of the TCO film having a resistivity substantially less than that of the second layer of the TCO film, and wherein the first layer of the TCO film is located closer to the front substrate than is the second layer of the TCO film.
16. A photovoltaic device comprising:
a front glass substrate;
a first layer comprising one or more of silicon nitride, silicon oxide, silicon oxynitride, and/or tin oxide;
a second layer comprising one or more of titanium oxide and/or niobium oxide, wherein at least the first layer is located between the front substrate and the second layer;
a third layer comprising metal oxide;
a conductive layer comprising silver and/or gold, wherein at least the third layer is provided between the conductive layer comprising silver and/or gold and the second layer; and
a transparent conductive oxide (TCO) film provided between the conductive layer comprising silver and/or gold and a semiconductor film of the photovoltaic device.
17. The photovoltaic device of claim 16, wherein the first layer has a refractive index (n) of from about 1.7 to 2.2, the second layer has a refractive index of from about 2.2 to 2.6, and wherein the second layer has a higher refractive index than the first layer.
18. The photovoltaic device of claim 16, wherein the TCO film comprises one or more of zinc oxide, zinc aluminum oxide, tin oxide, indium-tin-oxide, indium zinc oxide, tin antimony oxide, and zinc gallium aluminum oxide.
19. The photovoltaic device of claim 16, further comprising a buffer layer provided between the TCO film and the semiconductor film.
Description
  • [0001]
    This application is a continuation-in-part (CIP) of U.S. Ser. Nos. 11/898,641, filed Sep. 13, 2007, 11/591,668, filed Nov. 2, 2006, and 11/790,812, filed Apr. 27, 2007, the entire disclosures of which are all hereby incorporated herein by reference.
  • [0002]
    This invention relates to a photovoltaic device including an electrode such as a front electrode/contact. In certain example embodiments, the front electrode of the photovoltaic device includes a multi-layer coating having at least one infrared (IR) reflecting and conductive substantially metallic layer of or including silver, gold, or the like, and possibly at least one transparent conductive oxide (TCO) layer (e.g., of or including a material such as tin oxide, zinc oxide, or the like). In certain example embodiments, the multilayer front electrode coating is designed to realize one or more of the following advantageous features: (a) reduced sheet resistance and thus increased conductivity and improved overall photovoltaic module output power; (b) increased reflection of infrared (IR) radiation thereby reducing the operating temperature of the photovoltaic module so as to increase module output power; (c) reduced reflection and/or increased transmission of light in the region of from about 450-700 nm, and/or 450-600 nm, which leads to increased photovoltaic module output power; (d) reduced total thickness of the front electrode coating which can reduce fabrication costs and/or time; and/or (e) improved or enlarged process window in forming the TCO layer(s) because of the reduced impact of the TCO's conductivity on the overall electric properties of the module given the presence of the highly conductive substantially metallic IR reflecting layer(s).
  • BACKGROUND AND SUMMARY OF EXAMPLE EMBODIMENTS OF INVENTION
  • [0003]
    Photovoltaic devices are known in the art (e.g., see U.S. Pat. Nos. 6,784,361, 6,288,325, 6,613,603, and 6,123,824, the disclosures of which are hereby incorporated herein by reference). Amorphous silicon photovoltaic devices, for example, include a front electrode or contact. Typically, the transparent front electrode is made of a pyrolytic transparent conductive oxide (TCO) such as zinc oxide or tin oxide formed on a substrate such as a glass substrate. In many instances, the transparent front electrode is formed of a single layer using a method of chemical pyrolysis where precursors are sprayed onto the glass substrate at approximately 400 to 600 degrees C. Typical pyrolitic fluorine-doped tin oxide TCOs as front electrodes may be about 400 nm thick, which provides for a sheet resistance (Rs) of about 15 ohms/square. To achieve high output power, a front electrode having a low sheet resistance and good ohm-contact to the cell top layer, and allowing maximum solar energy in certain desirable ranges into the absorbing semiconductor film, are desired.
  • [0004]
    Unfortunately, photovoltaic devices (e.g., solar cells) with only such conventional TCO front electrodes suffer from the following problems.
  • [0005]
    First, a pyrolitic fluorine-doped tin oxide TCO about 400 nm thick as the entire front electrode has a sheet resistance (Rs) of about 15 ohms/square which is rather high for the entire front electrode. A lower sheet resistance (and thus better conductivity) would be desired for the front electrode of a photovoltaic device. A lower sheet resistance may be achieved by increasing the thickness of such a TCO, but this will cause transmission of light through the TCO to drop thereby reducing output power of the photovoltaic device.
  • [0006]
    Second, conventional TCO front electrodes such as pyrolytic tin oxide allow a significant amount of infrared (IR) radiation to pass therethrough thereby allowing it to reach the semiconductor or absorbing layer(s) of the photovoltaic device. This IR radiation causes heat which increases the operating temperature of the photovoltaic device thereby decreasing the output power thereof.
  • [0007]
    Third, conventional TCO front electrodes such as pyrolytic tin oxide tend to reflect a significant amount of light in the region of from about 450-700 nm so that less than about 80% of useful solar energy reaches the semiconductor absorbing layer; this significant reflection of visible light is a waste of energy and leads to reduced photovoltaic module output power. Due to the TCO absorption and reflections of light which occur between the TCO (n about 1.8 to 2.0 at 550 nm) and the thin film semiconductor (n about 3.0 to 4.5), and between the TCO and the glass substrate (n about 1.5), the TCO coated glass at the front of the photovoltaic device typically allows less than 80% of the useful solar energy impinging upon the device to reach the semiconductor film which converts the light into electric energy.
  • [0008]
    Fourth, the rather high total thickness (e.g., 400 nm) of the front electrode in the case of a 400 nm thick tin oxide TCO, leads to high fabrication costs.
  • [0009]
    Fifth, the process window for forming a zinc oxide or tin oxide TCO for a front electrode is both small and important. In this respect, even small changes in the process window can adversely affect conductivity of the TCO. When the TCO is the sole conductive layer of the front electrode, such adverse affects can be highly detrimental.
  • [0010]
    Thus, it will be appreciated that there exists a need in the art for an improved front electrode for a photovoltaic device that can solve or address one or more of the aforesaid five problems.
  • [0011]
    In certain example embodiments of this invention, the front electrode of a photovoltaic device is comprised of a multilayer coating including at least one conductive substantially metallic IR reflecting layer (e.g., based on silver, gold, or the like), and optionally at least one transparent conductive oxide (TCO) layer (e.g., of or including a material such as tin oxide, zinc oxide, or the like). In certain example instances, the multilayer front electrode coating may include a plurality of TCO layers and/or a plurality of conductive substantially metallic IR reflecting layers arranged in an alternating manner in order to provide for reduced visible light reflections, increased conductivity, increased IR reflection capability, and so forth.
  • [0012]
    In certain example embodiments of this invention, a multilayer front electrode coating may be designed to realize one or more of the following advantageous features: (a) reduced sheet resistance (Rs) and thus increased conductivity and improved overall photovoltaic module output power; (b) increased reflection of infrared (IR) radiation thereby reducing the operating temperature of the photovoltaic module so as to increase module output power; (c) reduced reflection and increased transmission of light in the region(s) of from about 450-700 nm and/or 450-600 nm which leads to increased photovoltaic module output power; (d) reduced total thickness of the front electrode coating which can reduce fabrication costs and/or time; and/or (e) an improved or enlarged process window in forming the TCO layer(s) because of the reduced impact of the TCO's conductivity on the overall electric properties of the module given the presence of the highly conductive substantially metallic layer(s).
  • [0013]
    In certain example embodiments of this invention, there is provided a photovoltaic device comprising: a front glass substrate; a semiconductor film; a substantially transparent front electrode located between at least the front glass substrate and the semiconductor film; wherein the substantially transparent front electrode comprises, moving away from the front glass substrate toward the semiconductor film, at least a first substantially transparent layer that may or may not be conductive, a substantially metallic infrared (IR) reflecting layer comprising silver and/or gold, and a first transparent conductive oxide (TCO) film located between at least the IR reflecting layer and the semiconductor film.
  • [0014]
    In other example embodiments of this invention, there is provided an electrode adapted for use in an electronic device such as a photovoltaic device including a semiconductor film, the electrode comprising: an electrically conductive and substantially transparent multilayer electrode supported by a glass substrate; wherein the substantially transparent multilayer electrode comprises, moving away from the glass substrate, at least a first substantially transparent conductive substantially metallic infrared (IR) reflecting layer comprising silver and/or gold, and a first transparent conductive oxide (TCO) film.
  • [0015]
    In other example embodiments, there is provided a photovoltaic device comprising: a glass substrate; a semiconductor film; a substantially transparent electrode located between at least the substrate and the semiconductor film; and wherein the substantially transparent electrode comprises, moving away from the glass substrate toward the semiconductor film, at least a first substantially transparent conductive substantially metallic layer comprising silver, and a first transparent conductive oxide (TCO) film located between at least the layer comprising silver and the semiconductor film.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0016]
    FIG. 1 is a cross sectional view of an example photovoltaic device according to an example embodiment of this invention.
  • [0017]
    FIG. 2 is a refractive index (n) versus wavelength (nm) graph illustrating refractive indices (n) of glass, a TCO film, silver thin film, and hydrogenated silicon (in amorphous, micro- or poly-crystalline phase).
  • [0018]
    FIG. 3 is a percent transmission (T %) versus wavelength (nm) graph illustrating transmission spectra into a hydrogenated Si thin film of a photovoltaic device comparing examples of this invention versus a comparative example (TCO reference); this shows that the examples of this invention (Examples 1, 2 and 3) have increased transmission in the approximately 450-700 nm wavelength range and thus increased photovoltaic module output power, compared to the comparative example (TCO reference).
  • [0019]
    FIG. 4 is a percent reflection (R %) versus wavelength (nm) graph illustrating reflection spectra from a hydrogenated Si thin film of a photovoltaic device comparing the examples of this invention (Examples 1, 2 and 3 referred to in FIG. 3) versus a comparative example (TCO reference referred to in FIG. 3); this shows that the example embodiment of this invention have increased reflection in the IR range, thereby reducing the operating temperature of the photovoltaic module so as to increase module output power, compared to the comparative example. Because the same Examples 1-3 and comparative example (TCO reference) are being referred to in FIGS. 3 and 4, the same curve identifiers used in FIG. 3 are also used in FIG. 4.
  • [0020]
    FIG. 5 is a cross sectional view of the photovoltaic device according to Example 1 of this invention.
  • [0021]
    FIG. 6 is a cross sectional view of the photovoltaic device according to Example 2 of this invention.
  • [0022]
    FIG. 7 is a cross sectional view of the photovoltaic device according to Example 3 of this invention.
  • [0023]
    FIG. 8 is a cross sectional view of the photovoltaic device according to another example embodiment of this invention.
  • [0024]
    FIG. 9 is a cross sectional view of the photovoltaic device according to another example embodiment of this invention.
  • [0025]
    FIG. 10 is a cross sectional view of the photovoltaic device according to another example embodiment of this invention.
  • [0026]
    FIG. 11 is a cross sectional view of the photovoltaic device according to another example embodiment of this invention.
  • DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION
  • [0027]
    Referring now more particularly to the figures in which like reference numerals refer to like parts/layers in the several views.
  • [0028]
    Photovoltaic devices such as solar cells convert solar radiation into usable electrical energy. The energy conversion occurs typically as the result of the photovoltaic effect. Solar radiation (e.g., sunlight) impinging on a photovoltaic device and absorbed by an active region of semiconductor material (e.g., a semiconductor film including one or more semiconductor layers such as a-Si layers, the semiconductor sometimes being called an absorbing layer or film) generates electron-hole pairs in the active region. The electrons and holes may be separated by an electric field of a junction in the photovoltaic device. The separation of the electrons and holes by the junction results in the generation of an electric current and voltage. In certain example embodiments, the electrons flow toward the region of the semiconductor material having n-type conductivity, and holes flow toward the region of the semiconductor having p-type conductivity. Current can flow through an external circuit connecting the n-type region to the p-type region as light continues to generate electron-hole pairs in the photovoltaic device.
  • [0029]
    In certain example embodiments, single junction amorphous silicon (a-Si) photovoltaic devices include three semiconductor layers. In particular, a p-layer, an n-layer and an i-layer which is intrinsic. The amorphous silicon film (which may include one or more layers such as p, n and i type layers) may be of hydrogenated amorphous silicon in certain instances, but may also be of or include hydrogenated amorphous silicon carbon or hydrogenated amorphous silicon germanium, or the like, in certain example embodiments of this invention. For example and without limitation, when a photon of light is absorbed in the i-layer it gives rise to a unit of electrical current (an electron-hole pair). The p and n-layers, which contain charged dopant ions, set up an electric field across the i-layer which draws the electric charge out of the i-layer and sends it to an optional external circuit where it can provide power for electrical components. It is noted that while certain example embodiments of this invention are directed toward amorphous-silicon based photovoltaic devices, this invention is not so limited and may be used in conjunction with other types of photovoltaic devices in certain instances including but not limited to devices including other types of semiconductor material, single or tandem thin-film solar cells, CdS and/or CdTe (including CdS/CdTe) photovoltaic devices, polysilicon and/or microcrystalline Si photovoltaic devices, and the like.
  • [0030]
    FIG. 1 is a cross sectional view of a photovoltaic device according to an example embodiment of this invention. The photovoltaic device includes transparent front glass substrate 1 (other suitable material may also be used for the substrate instead of glass in certain instances), optional dielectric layer(s) 2, multilayer front electrode 3, active semiconductor film 5 of or including one or more semiconductor layers (such as pin, pn, pinpin tandem layer stacks, or the like), back electrode/contact 7 which may be of a TCO or a metal, an optional encapsulant 9 or adhesive of a material such as ethyl vinyl acetate (EVA) or the like, and an optional superstrate 11 of a material such as glass. Of course, other layer(s) which are not shown may also be provided in the device. Front glass substrate 1 and/or rear superstrate (substrate) 11 may be made of soda-lime-silica based glass in certain example embodiments of this invention; and it may have low iron content and/or an antireflection coating thereon to optimize transmission in certain example instances. While substrates 1, 11 may be of glass in certain example embodiments of this invention, other materials such as quartz, plastics or the like may instead be used for substrate(s) 1 and/or 11. Moreover, superstrate 11 is optional in certain instances. Glass 1 and/or 11 may or may not be thermally tempered and/or patterned in certain example embodiments of this invention. Additionally, it will be appreciated that the word “on” as used herein covers both a layer being directly on and indirectly on something, with other layers possibly being located therebetween.
  • [0031]
    Dielectric layer(s) 2 may be of any substantially transparent material such as a metal oxide and/or nitride which has a refractive index of from about 1.5 to 2.5, more preferably from about 1.6 to 2.5, more preferably from about 1.6 to 2.2, more preferably from about 1.6 to 2.0, and most preferably from about 1.6 to 1.8. However, in certain situations, the dielectric layer 2 may have a refractive index (n) of from about 2.3 to 2.5. Example materials for dielectric layer 2 include silicon oxide, silicon nitride, silicon oxynitride, zinc oxide, tin oxide, titanium oxide (e.g., TiO2), aluminum oxynitride, aluminum oxide, or mixtures thereof. Dielectric layer(s) 2 functions as a barrier layer in certain example embodiments of this invention, to reduce materials such as sodium from migrating outwardly from the glass substrate 1 and reaching the IR reflecting layer(s) and/or semiconductor. Moreover, dielectric layer 2 is material having a refractive index (n) in the range discussed above, in order to reduce visible light reflection and thus increase transmission of visible light (e.g., light from about 450-700 nm and/or 450-600 nm) through the coating and into the semiconductor 5 which leads to increased photovoltaic module output power.
  • [0032]
    Still referring to FIG. 1, multilayer front electrode 3 in the example embodiment shown in FIG. 1, which is provided for purposes of example only and is not intended to be limiting, includes from the glass substrate 1 outwardly first transparent conductive oxide (TCO) or dielectric layer 3 a, first conductive substantially metallic IR reflecting layer 3 b, second TCO 3 c, second conductive substantially metallic IR reflecting layer 3 d, third TCO 3 e, and optional buffer layer 3 f. Optionally, layer 3 a may be a dielectric layer instead of a TCO in certain example instances and serve as a seed layer for the layer 3 b. This multilayer film 3 makes up the front electrode in certain example embodiments of this invention. Of course, it is possible for certain layers of electrode 3 to be removed in certain alternative embodiments of this invention (e.g., one or more of layers 3 a, 3 c, 3 d and/or 3 e may be removed), and it is also possible for additional layers to be provided in the multilayer electrode 3. Front electrode 3 may be continuous across all or a substantial portion of glass substrate 1, or alternatively may be patterned into a desired design (e.g., stripes), in different example embodiments of this invention. Each of layers/films 1-3 is substantially transparent in certain example embodiments of this invention.
  • [0033]
    First and second conductive substantially metallic IR reflecting layers 3 b and 3 d may be of or based on any suitable IR reflecting material such as silver, gold, or the like. These materials reflect significant amounts of IR radiation, thereby reducing the amount of IR which reaches the semiconductor film 5. Since IR increases the temperature of the device, the reduction of the amount of IR radiation reaching the semiconductor film 5 is advantageous in that it reduces the operating temperature of the photovoltaic module so as to increase module output power. Moreover, the highly conductive nature of these substantially metallic layers 3 b and/or 3 d permits the conductivity of the overall electrode 3 to be increased. In certain example embodiments of this invention, the multilayer electrode 3 has a sheet resistance of less than or equal to about 12 ohms/square, more preferably less than or equal to about 9 ohms/square, and even more preferably less than or equal to about 6 ohms/square. Again, the increased conductivity (same as reduced sheet resistance) increases the overall photovoltaic module output power, by reducing resistive losses in the lateral direction in which current flows to be collected at the edge of cell segments. It is noted that first and second conductive substantially metallic IR reflecting layers 3 b and 3 d (as well as the other layers of the electrode 3) are thin enough so as to be substantially transparent to visible light. In certain example embodiments of this invention, first and/or second conductive substantially metallic IR reflecting layers 3 b and/or 3 d are each from about 3 to 12 nm thick, more preferably from about 5 to 10 nm thick, and most preferably from about 5 to 8 nm thick. In embodiments where one of the layers 3 b or 3 d is not used, then the remaining conductive substantially metallic IR reflecting layer may be from about 3 to 18 nm thick, more preferably from about 5 to 12 nm thick, and most preferably from about 6 to 11 nm thick in certain example embodiments of this invention. These thicknesses are desirable in that they permit the layers 3 b and/or 3 d to reflect significant amounts of IR radiation, while at the same time being substantially transparent to visible radiation which is permitted to reach the semiconductor 5 to be transformed by the photovoltaic device into electrical energy. The highly conductive IR reflecting layers 3 b and 3 d attribute to the overall conductivity of the electrode 3 much more than the TCO layers; this allows for expansion of the process window(s) of the TCO layer(s) which has a limited window area to achieve both high conductivity and transparency.
  • [0034]
    First, second, and third TCO layers 3 a, 3 c and 3 e, respectively, may be of any suitable TCO material including but not limited to conducive forms of zinc oxide, zinc aluminum oxide, tin oxide, indium-tin-oxide, indium zinc oxide (which may or may not be doped with silver), or the like. These layers are typically substoichiometric so as to render them conductive as is known in the art. For example, these layers are made of material(s) which gives them a resistance of no more than about 10 ohm-cm (more preferably no more than about 1 ohm-cm, and most preferably no more than about 20 mohm-cm). One or more of these layers may be doped with other materials such as fluorine, aluminum, antimony or the like in certain example instances, so long as they remain conductive and substantially transparent to visible light. In certain example embodiments of this invention, TCO layers 3 c and/or 3 e are thicker than layer 3 a (e.g., at least about 5 nm, more preferably at least about 10, and most preferably at least about 20 or 30 nm thicker). In certain example embodiments of this invention, TCO layer 3 a is from about 3 to 80 nm thick, more preferably from about 5-30 nm thick, with an example thickness being about 10 nm. Optional layer 3 a is provided mainly as a seeding layer for layer 3 b and/or for antireflection purposes, and its conductivity is not as important as that of layers 3 b-3 e (thus, layer 3 a may be a dielectric instead of a TCO in certain example embodiments). In certain example embodiments of this invention, TCO layer 3 c is from about 20 to 150 nm thick, more preferably from about 40 to 120 nm thick, with an example thickness being about 74-75 nm. In certain example embodiments of this invention, TCO layer 3 e is from about 20 to 180 nm thick, more preferably from about 40 to 130 nm thick, with an example thickness being about 94 or 115 nm. In certain example embodiments, part of layer 3 e, e.g., from about 1-25 nm or 5-25 nm thick portion, at the interface between layers 3 e and 5 may be replaced with a low conductivity high refractive index (n) film 3 f such as titanium oxide to enhance transmission of light as well as to reduce back diffusion of generated electrical carriers; in this way performance may be further improved.
  • [0035]
    In certain example embodiments of this invention, the photovoltaic device may be made by providing glass substrate 1, and then depositing (e.g., via sputtering or any other suitable technique) multilayer electrode 3 on the substrate 1. Thereafter the structure including substrate 1 and front electrode 3 is coupled with the rest of the device in order to form the photovoltaic device shown in FIG. 1. For example, the semiconductor layer 5 may then be formed over the front electrode on substrate 1. Alternatively, the back contact 7 and semiconductor 5 may be fabricated/formed on substrate 11 (e.g., of glass or other suitable material) first; then the electrode 3 and dielectric 2 may be formed on semiconductor 5 and encapsulated by the substrate 1 via an adhesive such as EVA.
  • [0036]
    The alternating nature of the TCO layers 3 a, 3 c and/or 3 e, and the conductive substantially metallic IR reflecting layers 3 b and/or 3 d, is also advantageous in that it also one, two, three, four or all of the following advantages to be realized: (a) reduced sheet resistance (Rs) of the overall electrode 3 and thus increased conductivity and improved overall photovoltaic module output power; (b) increased reflection of infrared (IR) radiation by the electrode 3 thereby reducing the operating temperature of the semiconductor 5 portion of the photovoltaic module so as to increase module output power; (c) reduced reflection and increased transmission of light in the visible region of from about 450-700 nm (and/or 450-600 nm) by the front electrode 3 which leads to increased photovoltaic module output power; (d) reduced total thickness of the front electrode coating 3 which can reduce fabrication costs and/or time; and/or (e) an improved or enlarged process window in forming the TCO layer(s) because of the reduced impact of the TCO's conductivity on the overall electric properties of the module given the presence of the highly conductive substantially metallic layer(s).
  • [0037]
    The active semiconductor region or film 5 may include one or more layers, and may be of any suitable material. For example, the active semiconductor film 5 of one type of single junction amorphous silicon (a-Si) photovoltaic device includes three semiconductor layers, namely a p-layer, an n-layer and an i-layer. The p-type a-Si layer of the semiconductor film 5 may be the uppermost portion of the semiconductor film 5 in certain example embodiments of this invention; and the i-layer is typically located between the p and n-type layers. These amorphous silicon based layers of film 5 may be of hydrogenated amorphous silicon in certain instances, but may also be of or include hydrogenated amorphous silicon carbon or hydrogenated amorphous silicon germanium, hydrogenated microcrystalline silicon, or other suitable material(s) in certain example embodiments of this invention. It is possible for the active region 5 to be of a double-junction or triple-junction type in alternative embodiments of this invention. CdTe may also be used for semiconductor film 5 in alternative embodiments of this invention.
  • [0038]
    Back contact, reflector and/or electrode 7 may be of any suitable electrically conductive material. For example and without limitation, the back contact or electrode 7 may be of a TCO and/or a metal in certain instances. Example TCO materials for use as back contact or electrode 7 include indium zinc oxide, indium-tin-oxide (ITO), tin oxide, and/or zinc oxide which may be doped with aluminum (which may or may not be doped with silver). The TCO of the back contact 7 may be of the single layer type or a multi-layer type in different instances. Moreover, the back contact 7 may include both a TCO portion and a metal portion in certain instances. For example, in an example multi-layer embodiment, the TCO portion of the back contact 7 may include a layer of a material such as indium zinc oxide (which may or may not be doped with silver), indium-tin-oxide (ITO), tin oxide, and/or zinc oxide closest to the active region 5, and the back contact may include another conductive and possibly reflective layer of a material such as silver, molybdenum, platinum, steel, iron, niobium, titanium, chromium, bismuth, antimony, or aluminum further from the active region 5 and closer to the superstrate 11. The metal portion may be closer to superstrate 11 compared to the TCO portion of the back contact 7.
  • [0039]
    The photovoltaic module may be encapsulated or partially covered with an encapsulating material such as encapsulant 9 in certain example embodiments. An example encapsulant or adhesive for layer 9 is EVA or PVB. However, other materials such as Tedlar type plastic, Nuvasil type plastic, Tefzel type plastic or the like may instead be used for layer 9 in different instances.
  • [0040]
    Utilizing the highly conductive substantially metallic IR reflecting layers 3 b and 3 d, and TCO layers 3 a, 3 c and 3 d, to form a multilayer front electrode 3, permits the thin film photovoltaic device performance to be improved by reduced sheet resistance (increased conductivity) and tailored reflection and transmission spectra which best fit photovoltaic device response. Refractive indices of glass 1, hydrogenated a-Si as an example semiconductor 5, Ag as an example for layers 3 b and 3 d, and an example TCO are shown in FIG. 2. Based on these refractive indices (n), predicted transmission spectra impinging into the semiconductor 5 from the incident surface of substrate 1 are shown in FIG. 3. In particular, FIG. 3 is a percent transmission (T %) versus wavelength (nm) graph illustrating transmission spectra into a hydrogenated Si thin film 5 of a photovoltaic device comparing Examples 1-3 of this invention (see Examples 1-3 in FIGS. 5-7) versus a comparative example (TCO reference). The TCO reference was made up of 3 mm thick glass substrate 1 and from the glass outwardly 30 nm of tin oxide, 20 nm of silicon oxide and 350 nm of TCO. FIG. 3 thus shows that the examples of this invention (Examples 1-3 shown in FIGS. 5-7) has increased transmission in the approximately 450-600 and 450-700 nm wavelength ranges and thus increased photovoltaic module output power, compared to the comparative example (TCO reference).
  • [0041]
    Example 1 shown in FIG. 5 and charted in FIGS. 3-4 was made up of 3 mm thick glass substrate 1, 16 nm thick TiO2 dielectric layer 2, 10 nm thick zinc oxide TCO doped with Al 3 a, 8 nm thick Ag IR reflecting layer 3 b, and 115 nm thick zinc oxide TCO doped with Al 3 e. Layers 3 c, 3 d and 3 f were not present in Example 1. Example 2 shown in FIG. 6 and charted in FIGS. 3-4 was made up of 3 mm thick glass substrate 1, 16 nm thick TiO2 dielectric layer 2, 10 nm thick zinc oxide TCO doped with Al 3 a, 8 nm thick Ag IR reflecting layer 3 b, 100 nm thick zinc oxide TCO doped with Al 3 e, and 20 nm thick titanium suboxide layer 3 f Example 3 shown in FIG. 7 and charted in FIGS. 3-4 was made up of 3 mm thick glass substrate 1, 45 nm thick dielectric layer 2, 10 nm thick zinc oxide TCO doped with Al 3 a, 5 nm thick Ag IR reflecting layer 3 b, 75 nm thick zinc oxide TCO doped with Al 3 c, 7 nm thick Ag IR reflecting layer 3 d, 95 nm thick zinc oxide TCO doped with Al 3 e, and 20 nm thick titanium suboxide layer 3 f. These single and double-silver layered coatings of Examples 1-3 had a sheet resistance less than 10 ohms/square and 6 ohms/square, respectively, and total thicknesses much less than the 400 nm thickness of the prior art. Examples 1-3 had tailored transmission spectra, as shown in FIG. 3, having more than 80% transmission into the semiconductor 5 in part or all of the wavelength range of from about 450-600 nm and/or 450-700 nm, where AM1.5 has the strongest intensity and photovoltaic devices may possibly have the highest or substantially the highest quantum efficiency.
  • [0042]
    Meanwhile, FIG. 4 is a percent reflection (R %) versus wavelength (nm) graph illustrating reflection spectra from a hydrogenated Si thin film of a photovoltaic device comparing Examples 1-3 versus the above mentioned comparative example; this shows that Examples 1-3 had increased reflection in the IR range thereby reducing the operating temperature of the photovoltaic modules so as to increase module output power, compared to the comparative example. In FIG. 4, the low reflection in the visible range of from about 450-600 nm and/or 450-700 nm (the cell's high efficiency range) is advantageously coupled with high reflection in the near and short IR range beyond about 1000 nm; the high reflection in the near and short IR range reduces the absorption of solar thermal energy that will result in a better cell output due to the reduced cell temperature and series resistance in the module. As shown in FIG. 4, the front glass substrate 1 and front electrode 3 taken together have a reflectance of at least about 45% (more preferably at least about 55%) in a substantial part or majority of a near to short IR wavelength range of from about 1000-2500 nm and/or 1000 to 2300 nm. In certain example embodiments, it reflects at least 50% of solar energy in the range of from 1000-2500 nm and/or 1200-2300 nm. In certain example embodiments, the front glass substrate and front electrode 3 taken together have an IR reflectance of at least about 45% and/or 55% in a substantial part or a majority of a near IR wavelength range of from about 1000-2500 nm, possibly from 1200-2300 nm. In certain example embodiments, it may block at least 50% of solar energy in the range of 1000-2500 nm.
  • [0043]
    While the electrode 3 is used as a front electrode in a photovoltaic device in certain embodiments of this invention described and illustrated herein, it is also possible to use the electrode 3 as another electrode in the context of a photovoltaic device or otherwise.
  • [0044]
    FIG. 8 is a cross sectional view of a photovoltaic device according to another example embodiment of this invention. An optional antireflective (AR) layer 1 a may be provided on the light incident side of the front glass substrate 1 in any embodiment of this invention, as indicated for example by AR layer(s) 1 a shown in FIG. 8 (e.g., see also FIGS. 9-10). The photovoltaic device in FIG. 8 includes glass substrate 1, dielectric layer(s) 2 (e.g., of or including one or more of silicon oxide, silicon oxynitride, silicon nitride, titanium oxide, niobium oxide, and/or the like) which may function as a sodium barrier for blocking sodium from migrating out of the front glass substrate 1, seed layer 4 b (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, indium zinc oxide, or the like) which may be a TCO or dielectric in different example embodiments, silver based IR reflecting layer 4 c, optional overcoat or contact layer 4 d (e.g., of or including an oxide of Ni and/or Cr, zinc oxide, zinc aluminum oxide, or the like) which may be a TCO, TCO 4 e (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, zinc tin oxide, indium tin oxide, indium zinc oxide, or the like), optional buffer layer 4 f (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, zinc tin oxide, indium tin oxide, indium zinc oxide, or the like) which may be conductive to some extent, semiconductor 5 (e.g., CdS/CdTe, a-Si, or the like), optional back contact, reflector and/or electrode 7, optional adhesive 9, and optional back glass substrate 11. It is noted that in certain example embodiments, layer 4 b may be the same as layer 3 a described above, layer 4 c may be the same as layer 3 b or 3 d described above this applies to FIGS. 8-10), layer 4 e may be the same as layer 3 e described above (this also applies to FIGS. 8-10), and layer 4 f may be the same as layer 3 f described above (this also applies to FIGS. 8-10) (see descriptions above as to other embodiments in this respect). Likewise, layers 1, 5, 7, 9 and 11 are also discussed above in connection with other embodiments.
  • [0045]
    For purposes of example only, an example of the FIG. 8 embodiment is as follows (note that certain optional layers shown in FIG. 8 are not used in this example). For example, referring to FIG. 8, glass substrate 1 (e.g., about 3.2 mm thick), dielectric layer 2 (e.g., silicon oxynitride about 20 nm thick possibly followed by dielectric TiOx about 20 nm thick), Ag seed layer 4 b (e.g., dielectric or TCO zinc oxide or zinc aluminum oxide about 10 nm thick), IR reflecting layer 4 c (silver about 5-8 nm thick), TCO 4 e (e.g., conductive zinc oxide, tin oxide, zinc aluminum oxide, ITO from about 50-250 nm thick, more preferably from about 100-150 nm thick), and possibly conductive buffer layer 4 f (TCO zinc oxide, tin oxide, zinc aluminum oxide, ITO, or the like, from about 10-50 nm thick). In certain example embodiments, the buffer layer 4 f (or 3 f) is designed to have a refractive index (n) of from about 2.1 to 2.4, more preferably from about 2.15 to 2.35, for substantial index matching to the semiconductor 5 (e.g., CdS or the like) in order to improve efficiency of the device.
  • [0046]
    The photovoltaic device of FIG. 8 may have a sheet resistance of no greater than about 18 ohms/square, more preferably no greater than about 15 ohms/square, even more preferably no greater than about 13 ohms/square in certain example embodiments of this invention. Moreover, the FIG. 8 embodiment may have tailored transmission spectra having more than 80% transmission into the semiconductor 5 in part or all of the wavelength range of from about 450-600 nm and/or 450-700 nm, where AM1.5 may have the strongest intensity and in certain example instances the cell may have the highest or substantially the highest quantum efficiency.
  • [0047]
    FIG. 9 is a cross sectional view of a photovoltaic device according to yet another example embodiment of this invention. The photovoltaic device of the FIG. 9 embodiment includes optional antireflective (AR) layer 1 a on the light incident side of the front glass substrate 1, first dielectric layer 2 a, second dielectric layer 2 b, third dielectric layer 2 c which may optionally function as a seed layer (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, indium zinc oxide, or the like) for the silver based layer 4 c, conductive silver based IR reflecting layer 4 c, optional overcoat or contact layer 4 d (e.g., of or including an oxide of Ni and/or Cr, zinc oxide, zinc aluminum oxide, or the like) which may be a TCO or dielectric, TCO 4 e (e.g., including one or more layers, such as of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, zinc tin oxide, indium tin oxide, indium zinc oxide, or the like), optional buffer layer 4 f (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, zinc tin oxide, indium tin oxide, indium zinc oxide, or the like) which may be conductive to some extent, semiconductor 5 (e.g., one or more layers such as CdS/CdTe, a-Si, or the like), optional back contact, reflector and/or electrode 7, optional adhesive 9, and optional back/rear glass substrate 11. Semiconductor film 5 may include a single pin or pn semiconductor structure, or a tandem semiconductor structure in different embodiments of this invention. Semiconductor 5 may be of or include silicon in certain example instances. In other example embodiments, semiconductor film 5 may include a first layer of or including CdS (e.g., window layer) adjacent or closest to layer(s) 4 e and/or 4 f and a second semiconductor layer of or including CdTe (e.g., main absorber) adjacent or closest to the back electrode or contact 7.
  • [0048]
    Referring to the FIG. 9 embodiment (and the FIG. 10 embodiment), in certain example embodiments, first dielectric layer 2 a has a relatively low refractive index (n) (e.g., n of from about 1.7 to 2.2, more preferably from about 1.8 to 2.2, still more preferably from about 1.95 to 2.1, and most preferably from about 2.0 to 2.08), second dielectric layer 2 b has a relatively high (compared to layer 2 a) refractive index (n) (e.g., n of from about 2.2 to 2.6, more preferably from about 2.3 to 2.5, and most preferably from about 2.35 to 2.45), and third dielectric layer 2 c has a relatively low (compared to layer 2 b) refractive index (n) (e.g., n of from about 1.8 to 2.2, more preferably from about 1.95 to 2.1, and most preferably from about 2.0 to 2.05). In certain example embodiments, the first low index dielectric layer 2 a may be of or include silicon nitride, silicon oxynitride, or any other suitable material, the second high index dielectric layer 2 b may be of or include an oxide of titanium (e.g., TiO2 or the like), and the third dielectric layer 2 c may be of or include zinc oxide or any other suitable material. In certain example embodiments, layers 2 a-2 c combine to form a good index matching stack which also functions as a buffer against sodium migration from the glass 1. In certain example embodiments, the first dielectric layer 2 a is from about 5-30 nm thick, more preferably from about 10-20 nm thick, the second dielectric layer 2 b is from about 5-30 nm thick, more preferably from about 10-20 nm thick, and the third layer 2 c is of a lesser thickness and is from about 3-20 nm thick, more preferably from about 5-15 nm thick, and most preferably from about 6-14 nm thick. While layers 2 a, 2 b and 2 c are dielectrics in certain embodiments of this invention, one, two or all three of these layers may be dielectric or TCO in certain other example embodiments of this invention. Layers 2 b and 2 c are metal oxides in certain example embodiments of this invention, whereas layer 2 a is a metal oxide and/or nitride, or silicon nitride in certain example instances. Layers 2 a-2 c may be deposited by sputtering or any other suitable technique.
  • [0049]
    Still referring to the FIG. 9 embodiment (and the FIG. 10-11 embodiments), the TCO layer(s) 4 e may be of or include any suitable TCO including but not limited to zinc oxide, zinc aluminum oxide, tin oxide and/or the like. TCO layer or file 4 e may include multiple layers in certain example instances. For example, certain instances, the TCO 4 includes a first layer of a first TCO metal oxide (e.g., zinc oxide) adjacent Ag 4 c, Ag overcoat 4 d and a second layer of a second TCO metal oxide (e.g., tin oxide) adjacent and contacting layer 4 f and/or 5.
  • [0050]
    For purposes of example only, an example of the FIG. 9 embodiment is as follows. For example, referring to FIG. 9, glass substrate 1 (e.g., float glass about 3.2 mm thick, and a refractive index n of about 1.52), first dielectric layer 2 a (e.g., silicon nitride about 15 nm thick, having a refractive index n of about 2.07), second dielectric layer 2 b (e.g., oxide of Ti, such as TiO2 or other suitable stoichiometry, about 16 nm thick, having a refractive index n of about 2.45), third dielectric layer 2 c (e.g., zinc oxide, possibly doped with Al, about 9 nm thick, having a refractive index n of about 2.03), IR reflecting layer 4 c (silver about 5-8 nm thick, e.g., 6 nm), silver overcoat 4 d of NiCrOx about 1-3 nm thick which may or may not be oxidation graded, TCO film 4 e (e.g., conductive zinc oxide, zinc aluminum oxide and/or tin oxide about 10-150 nm thick), a semiconductor film 5 including a first layer of CdS (e.g., about 70 nm) closest to substrate 1 and a second layer of CdTe further from substrate 1, back contact or electrode 7, optional adhesive 9, and optionally substrate 11.
  • [0051]
    The photovoltaic device of FIG. 9 (and/or FIGS. 10-11) may have a sheet resistance of no greater than about 18 ohms/square, more preferably no greater than about 15 ohms/square, even more preferably no greater than about 13 ohms/square in certain example embodiments of this invention. Moreover, the FIG. 9 (and/or FIGS. 10-11) embodiment may have tailored transmission spectra having more than 80% transmission into the semiconductor 5 in part or all of the wavelength range of from about 450-600 nm and/or 450-700 nm, where AM1.5 may have the strongest intensity.
  • [0052]
    FIG. 10 is a cross sectional view of a photovoltaic device according to still another example embodiment of this invention. The FIG. 10 embodiment is the same as the FIG. 9 embodiment discussed above, except for the TCO film 4 e. In the FIG. 10 embodiment, the TCO film 4 e includes a first layer 4 e′ of or including a first TCO metal oxide (e.g., zinc oxide, which may or may not be doped with Al or the like) adjacent and contacting layer 4 d and a second layer 4 e″ of a second TCO metal oxide (e.g., tin oxide) adjacent and contacting layer 4 f and/or 5 (e.g., layer 4 f may be omitted, as in previous embodiments). Layer 4 e′ is also substantially thicker than layer 4 e″ in certain example embodiments. In certain example embodiments, the first TCO layer 4 e′ has a resistivity which is less than that of the second TCO layer 4 e″. In certain example embodiments, the first TCO layer 4 e′ may be of zinc oxide, Al-doped zinc oxide, or ITO about 70-150 nm thick (e.g., about 110 nm) having a resistivity of no greater than about 1 ohm·cm, and the second TCO layer 4 e″ may be of tin oxide about 10-50 nm thick (e.g., about 30 nm) having a resistivity of from about 10-100 ohm·cm, possibly from about 2-100 ohm·cm. The first TCO layer 4 e′ is thicker and more conductive than the second TCO layer 4 e″ in certain example embodiments, which is advantageous as layer 4 e′ is closer to the conductive Ag based layer 4 c thereby leading to improved efficiency of the photovoltaic device. Moreover, this design is advantageous in that CdS of the film 5 adheres or sticks well to tin oxide which may be used in or for layer 4 e″. TCO layers 4 e′ and/or 4 e″ may be deposited by sputtering or any other suitable technique.
  • [0053]
    In certain example instances, the first TCO layer 4 e′ may be of or include ITO (indium tin oxide) instead of zinc oxide. In certain example instances, the ITO of layer 4 e′ may be about 90% In, 10% Sn, or alternatively about 50% In, 50% Sn.
  • [0054]
    The use of at least these three dielectrics 2 a-2 c is advantageous in that it permits reflections to be reduced thereby resulting in a more efficient photovoltaic device. Moreover, it is possible for the overcoat layer 4 d (e.g., of or including an oxide of Ni and/or Cr) to be oxidation graded, continuously or discontinuously, in certain example embodiments of this invention. In particular, layer 4 d may be designed so as to be more metallic (less oxided) at a location therein closer to Ag based layer 4 d than at a location therein further from the Ag based layer 4 d; this has been found to be advantageous for thermal stability reasons in that the coating does not degrade as much during subsequently high temperature processing which may be associated with the photovoltaic device manufacturing process or otherwise.
  • [0055]
    In certain example embodiments of this invention, it has been surprisingly found that a thickness of from about 120-160 nm, more preferably from about 130-150 nm (e.g., 140 nm), for the TCO film 4 e is advantageous in that the Jsc peaks in this range. For thinner TCO thicknesses, the Jsc decreases by as much as about 6.5% until it bottoms out at about a TCO thickness of about 60 nm. Below 60 nm, it increases again until at a TCO film 4 e thickness of about 15-35 nm (more preferably 20-30 nm) it is attractive, but such thin coatings may not be desirable in certain example non-limiting situations. Thus, in order to achieve a reduction in short circuit current density of CdS/CdTe photovoltaic devices in certain example instances, the thickness of TCO film 4 e may be provided in the range of from about 15-35 nm, or in the range of from about 120-160 nm or 130-150 nm.
  • [0056]
    FIG. 11 is a cross sectional view of a photovoltaic device according to still another example embodiment of this invention. The FIG. 11 embodiment is similar to the FIG. 9-10 embodiments discussed above, except for the differences shown in the figure. FIG. 11 is a cross sectional view of a photovoltaic device according to an example embodiment of this invention. The photovoltaic device of the FIG. 11 may include: optional antireflective (AR) layer 1 a on the light incident side of the front glass substrate 1; first dielectric layer 2 a of or including one or more of silicon nitride (e.g., Si3N4 or other suitable stoichiometry), silicon oxynitride, silicon oxide (e.g., SiO2 or other suitable stoichiometry), and/or tin oxide (e.g., SnO2 or other suitable stoichiometry); second dielectric layer 2 b of or including titanium oxide (e.g., TiO2 or other suitable stoichiometry) and/or niobium oxide; third layer 2 c (which may be a dielectric or a TCO) which may optionally function as a seed layer (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, indium zinc oxide, or the like) for the silver based layer 4 c; conductive silver based IR reflecting layer 4 c; overcoat or contact layer 4 d (which may be a dielectric or conductive) of or including an oxide of Ni and/or Cr, NiCr, Ti, an oxide of Ti, zinc aluminum oxide, or the like; TCO 4 e (e.g., including one or more layers) of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, zinc tin oxide, indium tin oxide, indium zinc oxide, and/or zinc gallium aluminum oxide; optional buffer layer 4 f which may be a TCO in certain instances (e.g., of or including zinc oxide, zinc aluminum oxide, tin oxide, tin antimony oxide, zinc tin oxide, indium tin oxide, indium zinc oxide, titanium oxide, or the like) and which may be conductive to some extent; semiconductor film 5 of or including one or more layers such as CdS/CdTe, a-Si, or the like (e.g., film 5 may be made up of a layer of or including CdS adjacent layer 4 f, and a layer of or including CdTe adjacent layer 7); optional back contact/electrode/reflector 7 of aluminum or the like; optional adhesive 9 of or including a polymer such as PVB; and optional back/rear glass substrate 11. In certain example embodiments of this invention, dielectric layer 2 a may be from about 10-20 nm thick, more preferably from about 12-18 nm thick; layer 2 b may be from about 10-20 nm thick, more preferably from about 12-18 nm thick; layer 2 c may be from about 5-20 nm thick, more preferably from about 5-15 nm thick (layer 2 c is thinner than one or both of layers 2 a and 2 b in certain example embodiments); layer 4 c may be from about 5-20 nm thick, more preferably from about 6-10 nm thick; layer 4 d may be from about 0.2 to 5 nm thick, more preferably from about 0.5 to 2 nm thick; TCO film 4 e may be from about 50-200 nm thick, more preferably from about 75-150 nm thick, and may have a resistivity of no more than about 100 mΩ in certain example instances; and buffer layer 4 f may be from about 10-50 nm thick, more preferably from about 20-40 nm thick and may have a resistivity of no more than about 1 MΩ-cm in certain example instances. Moreover, the surface of glass 1 closest to the sun may be patterned via etching or the like in certain example embodiments of this invention.
  • [0057]
    Optional buffer layer 4 f may provide substantial index matching between the semiconductor film 5 (e.g., CdS portion) to the TCO 4 e in certain example embodiments, in order to optimize total solar transmission reaching the semiconductor.
  • [0058]
    Still referring to the FIG. 11 embodiments, semiconductor film 5 may include a single pin or pn semiconductor structure, or a tandem semiconductor structure in different embodiments of this invention. Semiconductor 5 may be of or include silicon in certain example instances. In other example embodiments, semiconductor film 5 may include a first layer of or including CdS (e.g., window layer) adjacent or closest to layer(s) 4 e and/or 4 f and a second semiconductor layer of or including CdTe (e.g., main absorber) adjacent or closest to the back electrode or contact 7.
  • [0059]
    Also referring to FIG. 11, in certain example embodiments, first dielectric layer 2 a has a relatively low refractive index (n) (e.g., n of from about 1.7 to 2.2, more preferably from about 1.8 to 2.2, still more preferably from about 1.95 to 2.1, and most preferably from about 2.0 to 2.08), second dielectric layer 2 b has a relatively high (compared to layer 2 a) refractive index (n) (e.g., n of from about 2.2 to 2.6, more preferably from about 2.3 to 2.5, and most preferably from about 2.35 to 2.45), and third dielectric layer 2 c may optionally have a relatively low (compared to layer 2 b) refractive index (n) (e.g., n of from about 1.8 to 2.2, more preferably from about 1.95 to 2.1, and most preferably from about 2.0 to 2.05). In certain example embodiments, layers 2 a-2 c combine to form a good index matching stack for antireflection purposes and which also functions as a buffer against sodium migration from the glass 1. In certain example embodiments, the first dielectric layer 2 a is from about 5-30 nm thick, more preferably from about 10-20 nm thick, the second dielectric layer 2 b is from about 5-30 nm thick, more preferably from about 10-20 nm thick, and the third layer 2 c is of a lesser thickness and is from about 3-20 nm thick, more preferably from about 5-15 nm thick, and most preferably from about 6-14 nm thick. While layers 2 a, 2 b and 2 c are dielectrics in certain embodiments of this invention, one, two or all three of these layers may be dielectric or TCO in certain other example embodiments of this invention. Layers 2 b and 2 c are metal oxides in certain example embodiments of this invention, whereas layer 2 a is a metal oxide and/or nitride, or silicon nitride in certain example instances. Layers 2 a-2 c may be deposited by sputtering or any other suitable technique.
  • [0060]
    Still referring to the FIG. 11 embodiment, the TCO layer(s) 4 e may be of or include any suitable TCO including but not limited to zinc oxide, zinc aluminum oxide, tin oxide and/or the like. TCO layer or file 4 e may include multiple layers in certain example instances. For example, certain instances, the TCO 4 includes a first layer of a first TCO metal oxide (e.g., zinc oxide) adjacent Ag 4 c, Ag overcoat 4 d and a second layer of a second TCO metal oxide (e.g., tin oxide) adjacent and contacting layer 4 f and/or 5. The photovoltaic device of FIG. 11 may have a sheet resistance of no greater than about 18 ohms/square, more preferably no greater than about 15 ohms/square, even more preferably no greater than about 13 ohms/square in certain example embodiments of this invention. Moreover, the FIG. 11 embodiment may have tailored transmission spectra having more than 80% transmission into the semiconductor 5 in part or all of the wavelength range of from about 450-600 nm and/or 450-700 nm, where AM1.5 may have the strongest intensity, in certain example embodiments of this invention.
  • [0061]
    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3411934 *Apr 15, 1964Nov 19, 1968Ppg Industries IncMethod of producing tin oxide-cobalt oxide plural layers on glass articles
US4155781 *Apr 6, 1978May 22, 1979Siemens AktiengesellschaftMethod of manufacturing solar cells, utilizing single-crystal whisker growth
US4162505 *Apr 24, 1978Jul 24, 1979Rca CorporationInverted amorphous silicon solar cell utilizing cermet layers
US4163677 *Apr 28, 1978Aug 7, 1979Rca CorporationSchottky barrier amorphous silicon solar cell with thin doped region adjacent metal Schottky barrier
US4213798 *Apr 27, 1979Jul 22, 1980Rca CorporationTellurium schottky barrier contact for amorphous silicon solar cells
US4378460 *Aug 31, 1981Mar 29, 1983Rca CorporationMetal electrode for amorphous silicon solar cells
US4387960 *Mar 17, 1981Jun 14, 1983Minolta Camera Co. Ltd.Multi-layer anti-reflection coating
US4532373 *Mar 14, 1984Jul 30, 1985Agency Of Industrial Science & Technology, Ministry Of International Trade And IndustryAmorphous photovoltaic solar cell
US4554727 *May 22, 1984Nov 26, 1985Exxon Research & Engineering CompanyMethod for making optically enhanced thin film photovoltaic device using lithography defined random surfaces
US4598306 *Jul 28, 1983Jul 1, 1986Energy Conversion Devices, Inc.Barrier layer for photovoltaic devices
US4598396 *Apr 3, 1984Jul 1, 1986Itt CorporationDuplex transmission mechanism for digital telephones
US4663495 *Jun 4, 1985May 5, 1987Atlantic Richfield CompanyTransparent photovoltaic module
US4664748 *Oct 17, 1985May 12, 1987Fuji Electric Company Ltd.Surface roughening method
US4689438 *Oct 16, 1985Aug 25, 1987Sanyo Electric Co., Ltd.Photovoltaic device
US4931412 *Jun 21, 1988Jun 5, 1990Licentia Patent-Verwaltungs GmbhMethod of producing a thin film solar cell having a n-i-p structure
US4940495 *Dec 7, 1988Jul 10, 1990Minnesota Mining And Manufacturing CompanyPhotovoltaic device having light transmitting electrically conductive stacked films
US5091764 *Sep 28, 1989Feb 25, 1992Kanegafuchi Kagaku Kogyo Kabushiki KaishaSemiconductor device having a transparent electrode and amorphous semiconductor layers
US5110637 *Mar 3, 1989May 5, 1992Asahi Glass Company Ltd.Amorphous oxide film and article having such film thereon
US5131954 *Nov 25, 1991Jul 21, 1992United Solar Systems CorporationMonolithic solar cell array and method for its manufacturing
US5230746 *Mar 3, 1992Jul 27, 1993Amoco CorporationPhotovoltaic device having enhanced rear reflecting contact
US5256858 *Aug 29, 1991Oct 26, 1993Tomb Richard HModular insulation electrically heated building panel with evacuated chambers
US5326519 *Oct 31, 1991Jul 5, 1994Nils ClaussenProcess of preparing zirconium oxide-containing ceramic formed bodies
US5595825 *Sep 21, 1994Jan 21, 1997Saint-Gobain VitrageTransparent substrate provided with a stack of thin films acting on solar and/or infrared radiation
US5603778 *Apr 19, 1995Feb 18, 1997Canon Kabushiki KaishaMethod of forming transparent conductive layer, photoelectric conversion device using the transparent conductive layer, and manufacturing method for the photoelectric conversion device
US5650019 *Sep 30, 1994Jul 22, 1997Canon Kabushiki KaishaSolar cell module having a surface coating material of three-layered structure
US5667853 *Mar 21, 1996Sep 16, 1997Toppan Printing Co., Ltd.Multilayered conductive film, and transparent electrode substrate and liquid crystal device using the same
US5861189 *Jan 11, 1996Jan 19, 1999Pilkington PlcMethod for producing mirrors by surface activation and pyrolytic deposition
US5891556 *Feb 23, 1996Apr 6, 1999Saint-Gobain VitrageTransparent substrate with antireflection coating
US5964962 *Nov 13, 1996Oct 12, 1999Sharp Kabushiki KaishaSubstrate for solar cell and method for producing the same; substrate treatment apparatus; and thin film solar cell and method for producing the same
US5965246 *Jun 3, 1996Oct 12, 1999Saint-Gobain VitrageTransparent substrates coated with a stack of thin layers having reflection properties in the infrared and/or in the solar radiation range
US6020077 *Feb 7, 1997Feb 1, 2000Saint-Gobain VitrageTransparent substrate provided with a thin-film stack with properties in the infrared
US6037289 *Sep 13, 1996Mar 14, 2000Rhodia ChimieTitanium dioxide-based photocatalytic coating substrate, and titanium dioxide-based organic dispersions
US6046621 *Sep 26, 1997Apr 4, 2000Advanced Micro Devices, Inc.Differential signal generator with dynamic beta ratios
US6123824 *Dec 15, 1997Sep 26, 2000Canon Kabushiki KaishaProcess for producing photo-electricity generating device
US6187824 *Aug 25, 1999Feb 13, 2001Nyacol Nano Technologies, Inc.Zinc oxide sol and method of making
US6288325 *May 4, 2000Sep 11, 2001Bp Corporation North America Inc.Producing thin film photovoltaic modules with high integrity interconnects and dual layer contacts
US6344608 *Jun 28, 1999Feb 5, 2002Canon Kabushiki KaishaPhotovoltaic element
US6365823 *Jun 17, 1998Apr 2, 2002Kaneka CorporationSolar cell module and manufacturing method thereof
US6380480 *May 17, 2000Apr 30, 2002Nippon Sheet Glass Co., LtdPhotoelectric conversion device and substrate for photoelectric conversion device
US6406639 *Mar 16, 2001Jun 18, 2002Nippon Sheet Glass Co., Ltd.Method of partially forming oxide layer on glass substrate
US6433913 *Dec 22, 1999Aug 13, 2002Gentex CorporationElectro-optic device incorporating a discrete photovoltaic device and method and apparatus for making same
US6469438 *Dec 4, 2000Oct 22, 2002Idemitsu Kosan Co., Ltd.Organic electroluminescence device with prescribed optical path length
US6506622 *Nov 3, 2000Jan 14, 2003Canon Kabushiki KaishaMethod of manufacturing a photovoltaic device
US6613603 *Jul 21, 1998Sep 2, 2003Canon Kabushiki KaishaPhotovoltaic device, process for production thereof, and zinc oxide thin film
US6627322 *Nov 28, 2001Sep 30, 2003Samsung Sdi Co., Ltd.Functional film having optical and electrical properties
US6686050 *Jan 7, 2003Feb 3, 2004Guardian Industries Corp.Heat treatable low-E coated articles and methods of making same
US6746775 *Jul 8, 1999Jun 8, 2004Saint-Gobain VitrageGlazing with optical and/or energetic properties capable of being electrically controlled
US6747779 *Mar 17, 2000Jun 8, 2004Saint-Gobain Glass FranceElectrochemical device such as an electrically controlled system with variable optical and/or energy properties
US6784361 *Sep 20, 2001Aug 31, 2004Bp Corporation North America Inc.Amorphous silicon photovoltaic devices
US6844210 *Jul 25, 2002Jan 18, 2005Idemitsu Kosan Co., Ltd.Organic electroluminescence device and method of manufacturing same
US6852555 *Apr 14, 2000Feb 8, 2005Thin Film Electronics AsaMethod in the fabrication of organic thin-film semiconducting devices
US6933672 *Jan 24, 2003Aug 23, 2005Idemitsu Kosan Co., Ltd.Actively driven organic EL device and manufacturing method thereof
US6936347 *Oct 17, 2001Aug 30, 2005Guardian Industries Corp.Coated article with high visible transmission and low emissivity
US6987547 *Sep 9, 2003Jan 17, 2006Hannstar Display Corp.Liquid crystal display device
US6989280 *Feb 17, 2005Jan 24, 2006Au Optronics Corp.Organic light-emitting diode devices having reduced ambient-light reflection and method of making the same
US7012728 *Apr 8, 2004Mar 14, 2006Saint-Gobain Glass FranceElectrochemical device, such as an electrically controlled system with variable optical and/or energy properties
US7037869 *Feb 25, 2004May 2, 2006Guardian Industries Corp.Clear glass composition
US7087834 *Dec 31, 2003Aug 8, 2006Andrena, Inc.Apparatus and method for photovoltaic energy production based on internal charge emission in a solid-state heterostructure
US7090921 *Jul 16, 2004Aug 15, 2006Guardian Industries Corp.Low-e coating with high visible transmission
US7169722 *Sep 23, 2003Jan 30, 2007Guardian Industries Corp.Clear glass composition with high visible transmittance
US7317237 *Dec 22, 2004Jan 8, 2008Kyocera CorporationPhotovoltaic conversion device and method of manufacturing the device
US20020008192 *Jul 11, 2001Jan 24, 2002Sanyo Electric Co., Ltd.Photovoltaic device
US20030011047 *May 7, 2002Jan 16, 2003Cunningham Daniel W.Photovoltaic device
US20030064255 *Aug 31, 2001Apr 3, 2003Dannenberg Rand DavidAnti-reflection coatings and associated methods
US20030165693 *Mar 1, 2002Sep 4, 2003Klaus HartigThin film coating having transparent base layer
US20040038051 *Nov 20, 2001Feb 26, 2004Akira FujisawaConductive film, production method therefor, substrate provided with it and photo-electric conversion device
US20040086723 *Aug 8, 2003May 6, 2004Thomsen Scott V.Coated article with silicon oxynitride adjacent glass
US20040113146 *Sep 2, 2003Jun 17, 2004Brahim DahmaniMaterial for use in the manufacturing of luminous display devices
US20040187914 *Mar 24, 2004Sep 30, 2004Canon Kabushiki KaishaStacked photovoltaic element and method for producing the same
US20050016583 *Nov 27, 2002Jan 27, 2005Ulf BlieskeTransparent substrate comprising an electrode
US20050042460 *Apr 8, 2004Feb 24, 2005Centre Luxembourgeois De Recherches Pour Le Verre Et La Ceramique S.A. (C.R.V.C.)Coated article with tin oxide, silicon nitride and/or zinc oxide under IR reflecting layer and corresponding method
US20060065299 *Nov 14, 2005Mar 30, 2006Asahi Glass Company, LimitedTransparent conductive substrate for solar cells and method for producing the substrate
US20060099441 *Sep 3, 2003May 11, 2006Saint-Gobain Glass FranceDiffusing substrate
US20060169316 *Feb 3, 2005Aug 3, 2006Guardian Industries Corp.Solar cell low iron patterned glass and method of making same
US20060219988 *Jun 7, 2006Oct 5, 2006Sumitomo Metal Mining Co., Ltd.Transparent conductive thin film, process for producing the same, sintered target for producing the same, and transparent, electroconductive substrate for display panel, and organic electroluminescence device
US20060228564 *Apr 4, 2006Oct 12, 2006Eclipse Energy SystemsTransparent Electrode
US20070029187 *Mar 13, 2006Feb 8, 2007Guardian Industries Corp.Method of making thermally tempered coated article with transparent conductive oxide (TCO) coating and product made using same
US20070120045 *Aug 31, 2006May 31, 2007Fuji Photo Film Co., Ltd.Organic photoelectric conversion device and stack type photoelectric conversion device
US20070184573 *Feb 8, 2006Aug 9, 2007Guardian Industries Corp.,Method of making a thermally treated coated article with transparent conductive oxide (TCO) coating for use in a semiconductor device
US20070193624 *Feb 23, 2006Aug 23, 2007Guardian Industries Corp.Indium zinc oxide based front contact for photovoltaic device and method of making same
US20070209698 *Oct 17, 2006Sep 13, 2007Thomsen Scott VLow iron high transmission float glass for solar cell applications and method of making same
US20070215205 *Mar 13, 2006Sep 20, 2007Guardian Industries Corp.Solar cell using low iron high transmission glass and corresponding method
US20080047602 *Aug 22, 2006Feb 28, 2008Guardian Industries Corp.Front contact with high-function TCO for use in photovoltaic device and method of making same
US20080047603 *Aug 24, 2006Feb 28, 2008Guardian Industries Corp.Front contact with intermediate layer(s) adjacent thereto for use in photovoltaic device and method of making same
US20080105293 *Apr 27, 2007May 8, 2008Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US20080105298 *Nov 2, 2006May 8, 2008Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US20080105299 *Nov 2, 2006May 8, 2008Guardian Industries Corp.Front electrode with thin metal film layer and high work-function buffer layer for use in photovoltaic device and method of making same
US20080105302 *Sep 13, 2007May 8, 2008Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US20080107799 *Apr 26, 2007May 8, 2008Guardian Industries Corp.Front electrode including transparent conductive coating on patterned glass substrate for use in photovoltaic device and method of making same
US20080163929 *Jan 8, 2007Jul 10, 2008Guardian Industries Corp.Zinc oxide based front electrode doped with yttrium for use in photovoltaic device or the like
US20080169021 *Jan 16, 2007Jul 17, 2008Guardian Industries Corp.Method of making TCO front electrode for use in photovoltaic device or the like
US20080178932 *Dec 3, 2007Jul 31, 2008Guardian Industries Corp.Front electrode including transparent conductive coating on patterned glass substrate for use in photovoltaic device and method of making same
US20080210303 *Feb 1, 2008Sep 4, 2008Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US20080223430 *Mar 14, 2007Sep 18, 2008Guardian Industries Corp.Buffer layer for front electrode structure in photovoltaic device or the like
US20080223436 *Mar 15, 2007Sep 18, 2008Guardian Industries Corp.Back reflector for use in photovoltaic device
US20090084438 *Sep 19, 2008Apr 2, 2009Guardian Industries Corp.,Front electrode for use in photovoltaic device and method of making same
US20090126791 *Nov 20, 2007May 21, 2009Guardian Industries Corp.Photovoltaic device including front electrode having titanium oxide inclusive layer with high refractive index
US20090194155 *Feb 1, 2008Aug 6, 2009Guardian Industries Corp.Front electrode having etched surface for use in photovoltaic device and method of making same
US20090194157 *Oct 2, 2008Aug 6, 2009Guardian Industries Corp.Front electrode having etched surface for use in photovoltaic device and method of making same
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7888594 *Nov 20, 2007Feb 15, 2011Guardian Industries Corp.Photovoltaic device including front electrode having titanium oxide inclusive layer with high refractive index
US7964788 *Apr 29, 2008Jun 21, 2011Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US8012317Apr 26, 2007Sep 6, 2011Guardian Industries Corp.Front electrode including transparent conductive coating on patterned glass substrate for use in photovoltaic device and method of making same
US8022291Sep 20, 2011Guardian Industries Corp.Method of making front electrode of photovoltaic device having etched surface and corresponding photovoltaic device
US8076571 *Dec 13, 2011Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US8203073 *Jun 19, 2012Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US8257561Sep 4, 2012Primestar Solar, Inc.Methods of forming a conductive transparent oxide film layer for use in a cadmium telluride based thin film photovoltaic device
US8334452Dec 18, 2012Guardian Industries Corp.Zinc oxide based front electrode doped with yttrium for use in photovoltaic device or the like
US8501522 *Aug 16, 2011Aug 6, 2013Gtat CorporationIntermetal stack for use in a photovoltaic cell
US8502066Nov 5, 2009Aug 6, 2013Guardian Industries Corp.High haze transparent contact including insertion layer for solar cells, and/or method of making the same
US8822260Mar 5, 2013Sep 2, 2014Gtat CorporationAsymmetric surface texturing for use in a photovoltaic cell and method of making
US8936842Nov 16, 2012Jan 20, 2015Guardian Industris Corp.Low-E coating having zinc aluminum oxide based layer doped with yttrium
US9153730Jul 12, 2010Oct 6, 2015First Solar, Inc.Solar cell front contact doping
US20080105302 *Sep 13, 2007May 8, 2008Guardian Industries Corp.Front electrode for use in photovoltaic device and method of making same
US20080308145 *Jun 12, 2007Dec 18, 2008Guardian Industries CorpFront electrode including transparent conductive coating on etched glass substrate for use in photovoltaic device and method of making same
US20110005591 *Jan 13, 2011First Solar, Inc.Solar Cell Front Contact Doping
US20110100445 *May 5, 2011Guardian Industries Corp.High haze transparent contact including insertion layer for solar cells, and/or method of making the same
US20110168252 *Dec 30, 2010Jul 14, 2011Guardian Industries Corp.Textured coating with etching-blocking layer for thin-film solar cells and/or methods of making the same
US20110186120 *Jan 26, 2011Aug 4, 2011Guardian Industries Corp.Textured coating with various feature sizes made by using multiple-agent etchant for thin-film solar cells and/or methods of making the same
US20120208317 *Aug 16, 2012Twin Creeks Technologies, Inc.Intermetal Stack for Use in a Photovoltaic Cell
CN102625953A *Jul 9, 2010Aug 1, 2012第一太阳能有限公司Solar cell front contact doping
CN103081026A *Mar 2, 2012May 1, 2013Lg化学株式会社Conductive structure and method for manufacturing same
WO2011008254A1 *Jul 9, 2010Jan 20, 2011First Solar, Inc.Solar cell front contact doping
WO2011126709A2 *Mar 18, 2011Oct 13, 2011First Solar, Inc.Doped buffer layer
WO2011126709A3 *Mar 18, 2011Jan 5, 2012First Solar, Inc.Doped buffer layer
Classifications
U.S. Classification136/256, 257/E31.126
International ClassificationH01L31/00
Cooperative ClassificationH01L31/022466, Y02E10/50, H01L31/1884
European ClassificationH01L31/0224C, H01L31/18J
Legal Events
DateCodeEventDescription
Feb 19, 2008ASAssignment
Owner name: GUARDIAN INDUSTRIES CORP., MICHIGAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:DEN BOER, WILLEM;LU, YIWEI;REEL/FRAME:020567/0611;SIGNING DATES FROM 20080118 TO 20080124